! LaTeX Error: Too many unprocessed floats.
See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help.
...
l.113 \includegraphics
[scale=0.5]{m2T4.pdf}
You've lost some text. Try typing <return> to proceed.
If that doesn't work, type X <return> to quit.
! Undefined control sequence.
\@float@Hx ...ltovf \fi \global \setbox \@currbox
\color@vbox \normalcolor \...
l.113 \includegraphics
[scale=0.5]{m2T4.pdf}
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
! Missing number, treated as zero.
<to be read again>
\vbox
l.113 \includegraphics
[scale=0.5]{m2T4.pdf}
A number should have been here; I inserted `0'.
(If you can't figure out why I needed to see a number,
look up `weird error' in the index to The TeXbook.)
pdfTeX warning: pdflatex (file ./m2T4.pdf): PDF inclusion: found PDF version <1
.5>, but at most version <1.4> allowed
<m2T4.pdf, id=1121, 538.28104pt x 212.1526pt>
File: m2T4.pdf Graphic file (type pdf)
<use m2T4.pdf>

LaTeX can, by default, only cope with 18 outstanding floats; any more, and you get the error “too many unsuppressed floats”. This package releases the limit; TeX itself imposes limits (which are interdependent of the help offered by e-TeX).
However, if your floats can’t be placed anywhere, extending the number of floats merely delays the arrival of the inevitable error message.